Valence-State-Engineered CuO/Carbon Nitride Heterojunction for Efficient CO2 Photoreduction to CH4

The photocatalytic conversion of CO2 into high-value-added chemicals such as CH4 is an effective approach to alleviating energy shortages and environmental problems. In this work, CuO/CN p–n heterojunction photocatalysts with distinct surface Cu valence-state distributions were prepared by varying the addition sequence of the Cu2+ precursor and NaOH. Among them, CuO/CN-1, prepared by adding the Cu2+ precursor first, possesses relatively more abundant surface Cu+ species and exhibits more efficient separation and migration of photogenerated charge carriers, achieving a CH4 evolution rate of 76.32 μmol·g−1, approximately 7.14 times that of pristine CN. The enhanced performance is mainly attributed to the synergistic effects of surface Cu valence-state regulation and p-n heterojunction construction. This work provides a new strategy for tailoring the interfacial electronic structure of CuO/CN toward highly selective photocatalytic CO2 reduction.